There are many situations in which defects in bones or portions of bones must be repaired or replaced, including fractures, joint degeneration, abnormal bone growth, infection and the like. For instance, a bone fracture may result in a portion of missing bone that must be replaced. Similarly, an infection may result in the removal of a portion of bone also requiring replacement.
Conventional bone replacement technologies have developed bone defect fillers for repairing bones by filling bone voids, gaps, cracks and the like. For instance, synthetic bone defect fillers, which are resorbable and porous, may replace bone with a bone-like mineral, e.g. crystalline hydroxyapatite or tricalcium phosphate. The resorbable and porous properties of these synthetic bone defect fillers allow for bone remodeling following implantation. However, conventional synthetic bone defect fillers are problematic because they may have poor tensile, flexural, and shear properties and may adhere poorly to the surrounding bone, which can result in washout of the bone defect filler from the bone defect prior to ingrowth of new bone into the bone defect filler.
Another conventional bone replacement technology includes bone defect fillers with a composition that maintains its chemical and mechanical properties without change or subsequent remodeling (e.g., titanium, stainless steel, PMMA). However, these permanent bone defect fillers are problematic because, inter alia, they are not resorbable and/or cannot be molded and shaped for in situ curing.
Another conventional bone replacement technology includes particulate polymers that can be mixed with blood to fill bone defects. These particulate polymer bone defect fillers are able to substantially conform to the shape of the bone defect, but they have no adhesive properties to adhere the particulate polymer to surrounding bone and, therefore, may wash out of the bone defect. Additionally, particulate polymer bone defect fillers are also problematic because they initially have no structural properties, e.g. tensile and compressive strength, after implantation.
Polyurethane bone defect fillers have also been developed for repairing bone defects. These polyurethane bone defect fillers may advantageously be applied to the bone defect and allowed to cure in situ to provide improved tensile strength and adhesive characteristics over other conventional synthetic bone defect fillers. Additionally, polyurethane bone defect fillers may be formed with a porous structure for promoting new bone ingrowth. However, polyurethane bone defect fillers may be difficult for a doctor to work because the polyurethane may expand as it cures and is typically applied while substantially liquid and, therefore, may fall/run out of the application site. Additionally, care must be taken while curing polyurethane bone defect fillers to avoid contamination, which can increase expansion, decrease adhesive characteristics and/or decrease mechanical strength. The porous structure formed by the polyurethane bone defect filler also typically lacks a high degree of pore interconnectivity, which, if increased, could better promote bone ingrowth after implantation.
Accordingly, there is a need for a polymeric bone defect filler providing increased bone growth promotion and improved handling, implantation and load supporting characteristics.